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Matlab Model Rf

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From the author

RF Toolbox and RF Blockset in MATLAB -- S-parameter I/O, network conversions (S/Z/Y/ABCD/T/H/G, mixed-mode), cascade/de-embedding, rfbudget analysis, circuit composition, matching networks, amplifier stability, mixer spurs, rational fitting, SI channels, baseband processing, Circuit Envelope simulation. Trigger: sparameters, Touchstone, .s2p, .s4p, rfplot, smithplot, rfparam, rfwrite, zparameters, yparameters, abcdparameters, s2sdd, cascadesparams, deembedsparams, rfbudget, noise figure, OIP3, IIP3, amplifier, modulator, nport, rffilter, attenuator, seriesRLC, shuntRLC, lcladder, txline, circuit, setports, clone, matchingnetwork, stabilityk, stabilitymu, powergain, gammams, gammaml, mixerIMT, OpenIF, rational, rationalfit, stepresp, txlineWRLGC, rf.Amplifier, rf.Mixer, rf.Filter, rf.Sparameter, rfsystem, RF Blockset.
— the description by MathWorks

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured approach to utilizing MATLAB's RF Toolbox and RF Blockset for end-to-end RF system development. It covers workflows ranging from measured S-parameter data validation and network conversions to complex circuit-level design, amplifier stability analysis, and time-domain Circuit Envelope simulation. The documentation emphasizes best practices for script-based workflows, proper element handling, and avoiding common pitfalls in RF parameter manipulation and system modeling.

What it does

  • Validates and processes measured S-parameter data from Touchstone files.
  • Performs network parameter conversions and mixed-mode analysis.
  • Enables RF signal chain design and cascaded budget analysis.
  • Supports circuit-level composition and impedance matching network design.
  • Facilitates amplifier stability analysis and mixer intermodulation planning.
  • Provides tools for rational fitting and time-domain system simulation.

When to use it

  • When working with measured S-parameter data for validation or de-embedding.
  • When designing RF signal chains and performing cascaded budget analysis.
  • When composing arbitrary RF circuits using node-based netlists.
  • When analyzing amplifier stability or mixer spur performance.
  • When performing time-domain signal integrity or Circuit Envelope simulations.

Advantages

  • Unified workflow for both passive and active RF device characterization.
  • Strict adherence to MATLAB identifier and object handling rules prevents silent errors.
  • Comprehensive support for modern visualization tools like tiledlayout and smithplot.
  • Clear separation between script-based design workflows and interactive analysis.
  • Detailed guidance on avoiding common errors in port ordering and parameter units.

Usage examples

“How do I load an S-parameter file and plot it on a Smith chart?”
The agent will guide you to use sparameters() to load the file, followed by smithplot() for visualization, ensuring you handle reference impedance correctly via newref() if needed.
“Calculate the cascaded gain and noise figure for my RF chain.”
The agent will help you define elements using rfbudget, ensuring you set the SignalBandwidth and use clone() for reused elements, then run the budget analysis.
“How do I analyze the stability of an amplifier?”
The agent will instruct you to use stabilityk and stabilitymu, and calculate power gain using powergain with the correct linear-to-dB conversion.
“I need to export my S-parameters to a new file.”
The agent will provide the rfwrite command, specifically reminding you to include 'ForceOverwrite', true to avoid interactive dialogs.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/matlab/matlab-model-rf/download

  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip matlab-model-rf.zip -d .agents/skills

Documentation by MathWorks

RF Toolbox and RF Blockset

Design, analyze, and simulate RF systems in MATLAB -- from measured S-parameter data through full time-domain Circuit Envelope simulation. One unified workflow covering passive networks, active device characterization, system cascade budgets, and behavioral time-domain modeling.

When to Use

Measured data workflows

  • Loading Touchstone files (.s1p through .snp), validating quality (passivity, causality, IEEE P370)

  • Plotting on Smith charts and rectangular plots, interpolating, re-referencing impedance

  • Converting between S, Z, Y, ABCD, T, H, G parameters; computing mixed-mode differential

  • Cascading and de-embedding S-parameter networks; fixture removal

System design and analysis

  • Building RF signal chains from behavioral elements (amplifier, modulator, rffilter, nport, etc.)

  • Computing cascaded gain, noise figure, IP3, SNR, output power with rfbudget

  • Comparing Friis vs Harmonic Balance solver accuracy

  • Exporting to RF Blockset Simulink models, Communications Toolbox, or MATLAB scripts

Circuit-level design

  • Composing arbitrary RF circuits with node wiring (SPICE-like netlist)

  • Designing impedance matching networks (L, Pi, Tee topologies, Richards stubs)

  • Analyzing amplifier stability (K-factor, mu), power gain, and matching conditions

  • Mixer intermodulation analysis and spur-free IF frequency planning

Time-domain and signal integrity

  • Fitting S-parameters to rational models; computing TDR, impulse, step responses

  • Exporting broadband circuit models to SPICE or Verilog-A

  • Building SI channel models from nport blocks, lossy transmission lines, and parasitics

  • Processing complex baseband signals through rf.Amplifier, rf.Mixer, rf.Filter System Objects

  • Full Circuit Envelope time-domain simulation via rfsystem (no Simulink knowledge required)

When NOT to Use

  • Antenna design and radiation patterns -- use Antenna Toolbox

  • RF propagation modeling (path loss, fading, ray tracing) -- use Communications Toolbox or Phased Array System Toolbox

  • SerDes/high-speed serial link equalization (FFE, CTLE, DFE, IBIS-AMI) -- use SerDes Toolbox

  • Radar waveform design or phased arrays -- use Phased Array System Toolbox

Must-Follow Rules

These apply across ALL RF Toolbox workflows. Violating them produces silent errors or blocks execution.

Universal

  1. rfwrite blocks on existing files -- Always pass 'ForceOverwrite', true. Without it, MATLAB opens an interactive overwrite dialog that halts unattended execution.

  2. Elements cannot be reused -- The same element object cannot appear twice in an rfbudget or circuit. Use clone(element) for independent copies.

  3. Element Name must be a valid MATLAB identifier -- No spaces, no special characters. Use 'IFAmp' not 'IF Amp'.

  4. Use tiledlayout/nexttile -- Not subplot. For all multi-panel figures.

  5. rfparam returns complex, not dB -- Always use 20*log10(abs(rfparam(...))) for dB magnitude.

S-Parameters and Network Parameters

  1. sparameters(filename, Z0) is invalid -- Cannot pass reference impedance at load time. Load first, then newref(s, Z0).

  2. rfinterp1 interpolates real/imag independently -- Not magnitude and angle. Can produce artifacts near sharp resonances.

  3. Frequency alignment required for cascade/de-embed -- cascadesparams and deembedsparams require identical frequency vectors. Always rfinterp1 to a common grid first.

  4. deembedsparams always requires 3 arguments -- (sMeasured, sFixture1, sFixture2). For one-sided, pass an ideal thru for the unused side.

  5. Mixed-mode port ordering is the #1 error source -- s2sdd option 1 (default) treats ports 1,2 as positive and 3,4 as negative. Verify which option matches your VNA port numbering.

  6. snp2smp argument order: ports before impedance -- snp2smp(s, portList, Z0), not snp2smp(s, Z0, portList).

rfbudget and Elements

  1. SignalBandwidth is required -- The 4th positional arg to rfbudget. Without it, NF/IP3/SNR remain empty.

  2. Passive NF equals loss -- For rfelement, NF should equal abs(Gain). Prefer attenuator which handles this automatically.

  3. nport Name is positional -- nport('file.s2p', 'MyName'), not name-value syntax.

  4. rffilter: ResponseType is shape, FilterType is algorithm -- rffilter('FilterType', 'Bandpass') errors. Use rffilter('ResponseType', 'Bandpass').

  5. show(b) opens a GUI -- Produces no command-window output. Use properties (b.TransducerGain, b.NF) for programmatic access.

Circuit Composition

  1. setports/setterminals can only be called once -- Plan topology before defining terminals.

  2. 2-port RF elements use 4-node mapping -- add(ckt, [in out inRef outRef], elem) for amplifier, modulator, nport, all txline types. Primitive 2-terminal elements (resistor, capacitor, inductor) use 2-node mapping.

  3. Primitive constructors are positional -- resistor(100, 'R1'), not resistor('Resistance', 100).

  4. setterminals takes a node vector -- setterminals(ckt, [1 2]), not setterminals(ckt, 1, 2).

  5. All txline constructors use name-value pairs only -- No positional arguments.

Amplifier Analysis

  1. powergain gain type string must be last -- powergain(s, 50, 50, 'Gt'), not powergain(s, 'Gt', 50, 50).

  2. powergain returns linear, not dB -- Convert with 10*log10(g) (power gain uses 10x, not 20x).

  3. Gmag returns NaN when conditionally stable -- Use Gmsg at frequencies where K < 1.

Rational Fitting

  1. rational vs rationalfit -- Use rational for new code (AAA). Use rationalfit only for delay extraction.

  2. Single-param fit returns plain vectors; multi-port returns cell arrays -- Always check with iscell(result).

  3. freqresp takes Hz -- Not rad/s. Pass s.Frequencies directly.

System Objects (rf.*)

  1. rf.Amplifier/rf.Mixer use 1-ohm power -- Vin = sqrt(Pin_W). This differs from rfsystem which uses 50-ohm.

  2. rf.Filter frequencies are ABSOLUTE RF -- PassFreq_bp=[2.395e9 2.405e9] means absolute GHz. Not baseband offsets.

  3. Properties locked during use -- Call release(obj) before modifying Nontunable properties.

rfsystem

  1. Requires rfbudget -- rfsystem takes an rfbudget, not raw elements.

  2. close_system needs save flag -- Use close_system(rfs, 0) to discard changes.

  3. IdealizedBaseband only supports amplifier/modulator/rffilter/nport -- Other elements require CircuitEnvelope.

Workflow Quick Reference

TaskEntry PointDetails
Load/plot S-parameterssparameters, rfplot, smithplotreference/sparameters-io.md
Convert S/Z/Y/ABCD, mixed-modezparameters, s2sdd, snp2smpreference/network-conversions.md
Cascade or de-embed networkscascadesparams, deembedsparamsreference/cascade-deembed.md
Create rfbudget elementsamplifier, modulator, rffilter, etc.reference/rfbudget-elements.md
Run cascade budget analysisrfbudget, rfplot(b, 'Pout')reference/rfbudget-analysis.md
Compose RF circuitscircuit, add, setportsreference/circuit-composition.md
Design matching networksmatchingnetwork, richardsreference/matching-networks.md
Analyze amplifier stability/gainstabilityk, powergain, gammamsreference/amplifier-analysis.md
Mixer spurs and IF planningmixerIMT, OpenIFreference/mixer-analysis.md
Fit rational models, TDRrational, stepresp, generateSPICEreference/rational-fitting.md
Build SI channel modelsnport + txlineWRLGC + circuitreference/si-channel-modeling.md
Process complex basebandrf.Amplifier, rf.Mixer, rf.Filterreference/baseband-processing.md
Time-domain system simulationrfsystem, Circuit Envelopereference/system-simulation.md

Conventions

Code Style

  • Use tiledlayout/nexttile for multi-panel figures (not subplot)

  • Always label axes with units (GHz, dB, ns, dBm) and include figure titles

  • Name elements descriptively for readable topology ('LNA', 'DCBlock', 'PCBTrace')

  • Use clone() liberally for element reuse

Script-First Workflow

For design, analysis, or sweep tasks -- write code to .m files on disk, not inline snippets. For quick one-off checks, inline evaluate_matlab_code is fine.

Modern APIs

  • tiledlayout/nexttile instead of subplot

  • datetime instead of datenum

  • rational instead of rationalfit (unless delay extraction needed)

  • smithplot instead of smith

  • rfplot for S-parameter visualization (handles dB conversion automatically)

References

Load the relevant reference file before writing code for a specific workflow. Each reference contains correct calling conventions, constructor arguments, property names, gotchas, and executable code patterns.

Copyright 2026 The MathWorks, Inc.

Files

reference/matching-networks.md

Impedance Matching Network Design

Design, evaluate, and optimize 1-port impedance matching networks. The matchingnetwork object and matchingNetworkDesigner app match a source impedance to a load impedance — they do not yet design 2-port (e.g., filter-style) matching. The object generates candidate topologies, ranks them by performance, and exports as circuit objects.

Creating a Matching Network

mn = matchingnetwork( ...
    'SourceImpedance', 50, ...
    'LoadImpedance', 75 + 20i, ...
    'CenterFrequency', 2.4e9, ...
    'Bandwidth', 200e6, ...
    'Components', 2);
Properties
PropertyDefaultDescription
SourceImpedance50Source impedance (see formats below)
LoadImpedance50Load impedance (see formats below)
CenterFrequency1e9Design frequency (Hz)
Bandwidth100e6Target bandwidth (Hz)
LoadedQ10Loaded Q factor
Components2Topology: 2, 3, 'L', 'Pi', 'Tee'
Circuit(auto)Read-only array of generated circuits
Bandwidth and LoadedQ Are Coupled

LoadedQ = CenterFrequency / Bandwidth. Setting one updates the other. If both are specified, Bandwidth takes precedence.

Components / Topology Options
ValueCircuits Generated
2 or 'L'2 L-section designs (series-L/shunt-C and series-C/shunt-L)
38 three-element designs (all permutations)
'Pi'4 shunt-series-shunt designs
'Tee'4 series-shunt-series designs

Gotcha: Maximum is 3 components. Components = 1 or Components = 4 error.

Impedance Source Formats

Both SourceImpedance and LoadImpedance accept:

% Scalar (constant impedance)
mn.LoadImpedance = 75 + 20i;

% S-parameter object (frequency-dependent, 1-port)
sAnt = sparameters('antenna.s1p');
mn.LoadImpedance = sAnt;

% Z-parameter or Y-parameter object
mn.LoadImpedance = zparameters(sAnt);

% Touchstone file path
mn.LoadImpedance = 'antenna.s1p';

% 1-port circuit object (must have setports called)
ckt = circuit('Load');
add(ckt, [1 0], resistor(75, 'RL'));
add(ckt, [1 0], capacitor(1e-12, 'CL'));
setports(ckt, [1 0]);
mn.LoadImpedance = ckt;

% Function handle (frequency in Hz)
mn.LoadImpedance = @(f) 50 + 30i*(f/1e9);

Inspecting Candidate Designs

[topology, performance] = circuitDescriptions(mn);
disp(topology);       % Component types and values for each design
disp(performance);    % Pass/fail, tests failed, performance score

The topology table columns: circuitName, component1Type, component1Value, component2Type, component2Value, etc. Component types are "Series L", "Series C", "Shunt L", "Shunt C".

The performance table columns: circuitName, evaluationPassed ("Yes"/"No"), testsFailed, performanceScore. Designs are ranked by score (descending). The performanceScore is a weighted composite — higher is better, but the scale depends on your evaluation parameters (it is not a fixed 0–100 range). Use it for relative ranking between candidates, not as an absolute quality metric.

Use component1Type/component2Type columns in the topology table to identify which topology each auto-generated design represents (e.g., "Series L" + "Shunt C" vs "Series C" + "Shunt L").

Evaluation Parameters

Add performance goals to rank and filter designs. Only two parameter types: 'gammain' (input reflection) and 'Gt' (transducer gain).

% Require return loss below -15 dB in-band
addEvaluationParameter(mn, 'gammain', '<', -15, [2.3e9 2.5e9], 2);

% Require insertion loss above -1 dB
addEvaluationParameter(mn, 'Gt', '>', -1, [2.3e9 2.5e9], 1);

% View current evaluations
params = getEvaluationParameters(mn);
disp(params);

% Remove an evaluation by row index
clearEvaluationParameter(mn, 1);

Arguments: (mn, parameter, comparison, targetdB, [fLow fHigh], weight) — all 6 are positional and required (weight is not optional).

A default automatic evaluation (Gt > -3 dB over [CenterFrequency - Bandwidth/2, CenterFrequency + Bandwidth/2]) is always present. Clear it with clearEvaluationParameter(mn, 1) if the automatic entry is at row 1.

Gotcha: Only 'gammain' and 'Gt' are supported — no S11, S21, VSWR, or other parameters.

Exporting Circuits

ckt = exportCircuits(mn);            % Best-ranked circuit only
ckts = exportCircuits(mn, [1 3]);    % Specific designs by index

Returns circuit objects containing inductor and capacitor elements. These can be used directly with sparameters(ckt, freq), embedded in larger circuits via add(), or cascaded.

Visualization

Frequency Response
rfplot(mn);                          % All designs, auto frequency range
rfplot(mn, freq);                    % Custom frequencies
rfplot(mn, freq, [1 3]);             % Specific designs

Plots two panels: input reflection coefficient (gammain) and transducer gain (Gt) in dB. Overlays evaluation goal lines.

Smith Chart
smithplot(mn);                                        % Best design
smithplot(mn, 'CircuitIndex', 2, 'Z0', 50);          % Specific design

Shows the impedance transformation path from source to load, tracing through each matching element in sequence (one arc per L/C component). This is the standard way to visualize each element's individual contribution to the match — no need to build intermediate circuits manually.

Gotcha: smithplot(mn) works directly on the matchingnetwork object. To plot an exported circuit's S-parameters on a Smith chart, use the S-parameter object form:

ckt = exportCircuits(mn);
s = sparameters(ckt, linspace(1e9, 3e9, 201));
smithplot(s, 1, 1);                                   % Plot S11

Do not pass the circuit object directly to smithplot — it only accepts matchingnetwork, sparameters, or numeric data.

S-Parameters
s = sparameters(mn);                       % Best design, auto frequency
s = sparameters(mn, freq);                 % Custom frequencies
s = sparameters(mn, freq, Z0);             % Custom reference impedance
sArr = sparameters(mn, freq, Z0, [1 3]);   % Multiple designs -> array

The 4-argument form sparameters(mn, freq, Z0, circuitIndex) extracts S-parameters directly without needing exportCircuits first. Use gammain(s) or powergain(s, 50, 50, 'Gt') on the result for analysis.

Richards Transformation (Lumped -> Stubs)

Convert lumped L/C matching elements to transmission line stubs. See reference/lumped-to-distributed.md for full Kuroda identity and realization details.

txCkt = richards(mn, 2.4e9);              % Best design at 2.4 GHz
txCkts = richards(mn, 2.4e9, [1 2]);      % Specific designs

Returns circuit objects with txlineElectricalLength stub elements. Each stub has:

  • Z0 — characteristic impedance (from original element)

  • LineLength — electrical length in radians (pi/4 for quarter-wave)

  • ReferenceFrequency — the operating frequency argument

  • Termination — 'Short' for inductors, 'Open' for capacitors

  • StubMode — 'Series' or 'Shunt' matching the original topology

Stub element names get a _tx suffix: C becomes C_tx, L becomes L_tx.

Tolerance Analysis

Evaluate matching network sensitivity to component value variations:

% Default 5% tolerance on all components
toleranceAnalysis(mn);

% Custom tolerances per component
toleranceAnalysis(mn, [0.05 0.02 0.10]);    % 5%, 2%, 10% for each component

% Custom frequency range and specific circuit
toleranceAnalysis(mn, 0.05, linspace(0.5e9, 2.5e9, 500), 1);

Arguments: (mn, tolerances, freqList, circuitIndices) — all optional after mn. Plots the nominal and perturbed responses showing the spread due to component variations.

Custom Matching Networks

Import user-designed circuits for comparison alongside auto-generated designs:

% Build a custom matching circuit
custom = circuit('MyMatch');
add(custom, [1 2], inductor(3.3e-9, 'Ls'));
add(custom, [2 0], capacitor(0.8e-12, 'Cp'));
setports(custom, [1 0], [2 0]);

% Add to matchingnetwork for evaluation
addNetwork(mn, custom);    % Appears as "user_1" in circuitDescriptions

% Remove a custom network by name
deleteNetwork(mn, 'user_1');

% Suppress auto-generated designs to evaluate only custom circuits
disableAutomaticNetworks(mn);

% Re-enable auto-generated designs
enableAutomaticNetworks(mn);

Custom networks appear as "user_1", "user_2", etc. in circuitDescriptions.

Gotcha: Custom circuits must be 2-port with setports called, and contain only R/L/C elements. Other element types produce -Inf performance scores.

Matching Network Designer App (R2021a+)

Interactive GUI for designing and comparing matching networks:

matchingNetworkDesigner              % Launch empty
matchingNetworkDesigner(mn)          % Pre-loaded with existing design

The app provides visual comparison of topologies, interactive evaluation parameter setup, and Smith chart visualization. Configure programmatically with matchingnetwork, then open in the designer for interactive exploration.

Handle Class Behavior

matchingnetwork is a handle class. These methods mutate in-place (no output argument):

  • addNetwork, deleteNetwork

  • disableAutomaticNetworks, enableAutomaticNetworks

Use copy(mn) for independent deep copies.

Gotchas

  1. Property is Bandwidth (lowercase 'w') — not BandWidth as some help text suggests.

  2. Components range is 2–3 only — Components = 1 or Components = 4 error.

  3. Only 'gammain' and 'Gt' evaluation parameters — no S11, S21, VSWR. All 6 positional arguments are required: (mn, parameter, comparison, targetdB, [fLow fHigh], weight).

  4. Handle class — addNetwork/deleteNetwork mutate in-place. Assigning their output errors ("too many output arguments").

  5. Custom circuits must be 2-port RLC only — other element types produce warnings and -Inf scores.

  6. Default automatic evaluation always present — Gt > -3 dB over bandwidth. Clear explicitly if unwanted.

  7. Bandwidth takes precedence over LoadedQ when both are specified.

  8. smithplot only accepts matchingnetwork or sparameters objects — do not pass a circuit object directly. For exported circuits, call sparameters(ckt, freq) first, then smithplot(s, 1, 1).

  9. performanceScore is relative, not absolute — use it to rank candidates against each other, not as a fixed quality metric. The scale depends on your evaluation parameters and weights.

Conventions

  • Use tiledlayout/nexttile for multi-panel matching analysis plots

  • Show smithplot alongside rfplot for matching network analysis

  • Always inspect circuitDescriptions to compare candidates before selecting

  • Label axes with units (GHz, dB) and include figure titles

Copyright 2026 The MathWorks, Inc.

Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Node.js

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Attribution and licence

Created by
MathWorks
Publisher
MathWorks (Official)
Source
matlab/matlab-agentic-toolkit · skills-catalog/rf-and-mixed-signal/matlab-model-rf · commit 2a7f215
Licence
BSD 2-Clause License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE.md)
  • ATTRIBUTION.md (written by AutoGineer)
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